Sulfuryl fluoride fumigation process

ABSTRACT

A process is provided for determining the amount of sulfuryl fluoride in the atmosphere of an enclosed area that has been fumigated with sulfuryl fluoride (SO 2 F 2 ). This process comprises: (A) sampling said atmosphere of said enclosed area to obtain a gaseous sample; (B) selectively removing water from said gaseous sample by passing said gaseous sample through a perevaporation zone to obtain a perevaporated sample, wherein said perevaporation zone comprises a copolymer of tetrafluoroethylene and perfluoro-3,6-dioxa-4-methyl-7-octene-sulfonic acid; and (C) analyzing said perevaporated sample in a sulfuryl fluoride detector to determine the amount of sulfuryl fluoride in said perevaporated sample.

BACKGROUND OF THE INVENTION

This invention is related to the field of fumigation processes that usesulfuryl fluoride as a fumigant.

It is well known that insects and other pests are very destructive toproperty and that they can endanger human life. It has been estimatedthat termites alone cause more than 750 million dollars in damage everyyear, much of this damage is done to homes where families live.

Fumigation is the use of certain gases to control insects and otherpests that are present in enclosed, or enclosable, areas where they arenot desired, such as, family homes. Currently, the fumigant of choice issulfuryl fluoride. The preferred source for sulfuryl fluoride is DowAgroSciences LLC., which sells a specialty sulfuryl fluoride productunder the trademark Vikane® gas fumigant.

During fumigation it is important to know the amount of sulfurylfluoride in the air of the enclosed area. This is because a certainlevel of sulfuryl fluoride is needed in the air of the enclosed area inorder to rid such area of the insects and other pests that are presenttherein. Consequently, a Fumiscope is used to determine this amount.

A Fumiscope is a portable instrument that will quantitatively measurethe gas concentration in air by sampling the atmosphere of the enclosedarea. However: there are certain problems with using a Fumiscope. Inparticular, most, if not all, Fumiscopes that measure sulfuryl fluorideare sensitive to the amount of water vapor in the air. That is, theamount of water vapor adversely affects the detection capabilities ofthe Fumiscope. One preferred method to overcome this problem is to use adrying material such as, anhydrous calcium sulfate to absorb the watervapor. However, this solution is not optimal. First, these types ofdryers can remove other gases, such as sulfuryl fluoride, from thesample thereby making the Fumiscope give an inaccurate reading. Second,these types of dryers are used up during the monitoring, andconsequently, the effectiveness of these dryers decreases over time andthe baseline of the Fumiscope drifts. This means that the dryers must bereplaced often during monitoring and the Fumiscope must be re-zeroedduring monitoring in order to get accurate readings. These proceduresare time consuming and labor-intensive and prevent the unattendedoperation of the Fumiscope.

Consequently, in light of the above the inventors provide the followingsolution to this problem.

BRIEF SUMMARY OF THE INVENTION

It is an object of this invention to provide a sulfuryl fluoridefumigation process.

In accordance with this invention a process is provided for determiningthe amount of sulfuryl fluoride in the atmosphere of an enclosed areathat has been fumigated with sulfuryl fluoride (SO₂F₂). This processcomprises:

-   -   (A) sampling said atmosphere of said enclosed area to obtain a        gaseous sample;    -   (B) selectively removing water from said gaseous sample by        passing said gaseous sample through a perevaporation zone to        obtain a perevaporated sample, wherein said perevaporation zone        comprises a copolymer of tetrafluoroethylene and        perfluoro-3,6-dioxa-4-methyl-7-octene-sulfonic acid; and    -   (C) analyzing said perevaporated sample in a sulfuryl fluoride        detector to determine the amount of sulfuryl fluoride in said        perevaporated sample.

Additional information on this invention is provided in detail in thefollowing.

DETAILED DESCRIPTION OF THE INVENTION

Fumigation is well known in the art. It can be conducted in any areathat is enclosed or enclosable. Specific examples are homes, officebuildings, and churches. For the purposes of this invention, thefumigant of choice is sulfuryl fluoride (SO₂F₂).

The first step in this invention is to sample the atmosphere of thesulfuryl-fluoride-fumigated-enclosed area to obtain a gaseous sample.This sampling can be conducted continuously or intermittently at thediscretion of the licensed fumigation operator.

The second step in the process is to selectively remove water from thegaseous sample. This is accomplished by passing the gaseous samplethrough a perevaporation zone. This produces a perevaporated sample. Theperevaporation zone comprises a membrane made from a copolymer oftetrafluoroethylene and perfluoro-3,6-dioxa-4-methyl-7-octene-sulfonicacid. Currently, it is preferred to use Nafion® copolymer because it ishighly selective in the removal of water from gases (Nafion® is aregistered trademark of E.I. DuPont). The sole supplier of Nafion tubingto the world is PermaPure Inc which has a web site at www.permapure.com.As the sample moves through the perevaporation zone, water isselectively removed from the sample. The water, so removed, then passesthrough the membrane wall of the copolymer where it evaporates into thesurrounding air.

The third step of the process is to analyze said perevaporated sample ina sulfuryl fluoride detector to determine the amount of sulfurylfluoride in said perevaporated sample. This analysis is conducted by asulfuryl fluoride detector that is sensitive to the presence of water inthe gaseous sample. One example of a sulfuryl fluoride detector is aFumiscope. One can obtain a Fumiscope that performs sulfuryl fluoridedetection from Key Chemical & Equipment Co. Inc., 13195 49th StreetNorth Unit A, Clearwater, Fla. 33762 USA. After the amount of sulfurylfluoride is determined, this value can be used to determine if asufficient quantity of sulfuryl fluoride is present in the air so thatthe enclosed area is properly fumigated.

During testing of a Fumiscope using a standard drying tube comprisinganhydrous calcium sulfate and one using a Nafion drying tube the resultswere extraordinary. The Fumiscope with the standard drying tube requiredchanging of the drying tube and constant re-zeroing of the Fumiscope inorder to take accurate readings. On the other hand, the Fumiscope thatused the Nafion tubing, which pulled the sample through the tubingbefore passing the perevaporated sample into the detector ran for weekswith no drift and no need to re-zero the instrument.

Additional side-by-side laboratory testing showed that a Fumiscope usinga standard drying tube comprising anhydrous calcium sulfate took longerto achieve the correct reading and took longer to re-zero than theFumiscope equipped with a Nafion drying tube.

Consequently, this invention gives more accurate readings and itprovides these reading quicker, and with less re-zeroing than theindustry standard.

1. A process for determining the amount of sulfuryl fluoride in theatmosphere of an enclosed area that has been fumigated with sulfurylfluoride (SO₂F₂) this process comprises: (A) sampling said atmosphere ofsaid enclosed area to obtain a gaseous sample; (B) selectively removingwater from said gaseous sample by passing said gaseous sample through aperevaporation zone to obtain a perevaporated sample, wherein saidperevaporation zone comprises a copolymer of tetrafluoroethylene andperfluoro-3,6-dioxa-4-methyl-7-octene-sulfonic acid; and (C) analyzingsaid perevaporated sample in a sulfuryl fluoride detector to determinethe amount of sulfuryl fluoride in said perevaporated sample.
 2. Aprocess comprising fumigating an enclosed area with sulfuryl fluoride(SO₂F₂) and then determining the concentration of sulfuryl fluoride(SO₂F₂) using a Fumiscope equipped with a perevaporation zone thatcomprises a copolymer of tetrafluoroethylene andperfluoro-3,6-dioxa-4-methyl-7-octene-sulfonic acid.
 3. A Fumiscopeequipped with a perevaporation zone that comprises a copolymer oftetrafluoroethylene and perfluoro-3,6-dioxa-4-methyl-7-octene-sulfonicacid.